The use of electrically conductive leads for the delivery of body stimulation energy is known to the prior art. Typically such leads employ one or more conductors insulated from the body environment, and themselves, by an insulating material with the conductors being in electrical communication with electrodes carried by the lead body. In the context of temporary cardiac pacing, it has become common practice to employ coaxial leads of a type having a multifilament inner conductor and a braided outer conductor separated by a sheath of insulation with the outer braided conductor also being insulated.
Typical coaxial leads of the type discussed above are provided with an electrode pair adjacent the distal end thereof, usually in the form of a ring electrode in electrical communication with the braided conductor and a tip electrode in electrical communication with the inner conductor. The positioning of the tip electrode and the establishment of electrical communication between it and the inner conductor is relatively straightforward. However, the prior art systems by which the ring electrode is positioned, and the electrical communication between it and the braided conductor is established, are cumbersome and not totally reliable.
In all known ring electrode placement systems, the first step is to strip the outermost insulation from the desired ring electrode location to that end of the lead at which the tip electrode will be positioned. In one system, following the stripping step, a ring having a larger inner diameter than the outer diameter of the braided conductor is then positioned at the desired ring electrode location. The excess braided conductor which extends between the positioned ring electrode and the lead end is then jammed under the ring electrode to establish a mechanical and electrical engagement between the braided conductor and the ring electrode. While this system allows the ring electrode to be positioned in the desired location with relative ease, the jamming of the braided conductor under the ring is potentially damaging to the braided conductor material and its effectiveness in establishing the mechanical and electrical connection cannot be viewed, inasmuch as the connection is obscured by the ring electrode itself.
Another system by which a ring electrode is positioned, and an electrical communication between it and the outer braided conductor is established, employs a ring underlying the braided conductor at the desired electrode location. This ring increases the braided conductor diameter at the desired electrode location. The desired electrode location is then coated with a silver epoxy and the ring electrode is threaded over the lead. The ring electrode has a diameter approximately equal to that of the braided conductor at the desired electrode location such that a force fit is established to maintain the electrode in position. The silver epoxy, being conductive, facilitates the electrical communication between the braided conductor and the ring electrode. While this system has proven commercially feasible, it nonetheless requires excessive manipulation. In addition, the use of silver epoxy requires a high degree of care so that it is contained within the desired electrode location.